This invention relates to a waveform display utilizing frequency-based coloring and navigation.
There are at least three well known representations of a signal:
1. The spectrum or frequency domain representation is a two-dimensional graph in which amplitude is plotted versus frequency. All points of the graph are normally plotted using the same color. Time information is not evident.
2. The spectrogram is a three-dimensional graph in which frequency is plotted versus time and the points of the graph are rendered using colors or shades of gray to convey amplitude information.
3. The waveform display or time domain representation is a two-dimensional graph in which amplitude is plotted versus time. All points of the graph are normally plotted using the same color. Frequency information is not evident.
FIG. 1 shows a portion 10 of a typical waveform display derived from an audio signal, i.e. an electrical signal containing audio frequency components. The waveform display shown in FIG. 1 is of the kind that might be presented by a display device having a display area composed of pixels 14 arranged in columns 18. For convenience, the pixels 14 are shown in FIG. 1 as having an aspect ratio (height: width) substantially less than one, but in practice the aspect ratio would normally be closer to one.
By way of example, the portion 10 of the waveform display represents an audio signal that has been sampled at intervals .tau. and has been quantized to return the twenty values indicated at the bottom of FIG. 1. Each column 18 of pixels is used to display a representation of the evolution of the signal over an interval 5.tau., so that the twenty sample values are represented by four columns. Typically, the background color of the display is white and the amplitude information is plotted by rendering selected pixels 14 with a contrasting foreground color or black. The pixels in the column that are rendered with the foreground color (or black) show a line segment connecting the maximum and minimum sample values within the interval represented by the column. Thus, in the leftmost column the pixels from -2 to +5 are rendered with the foreground color (or black), represented by solid diagonal shading.